A constant temperature liquid circulating device including a conduit for delivering circulating liquid controlled to a constant temperature with a pump, wherein both ends of a piping that defines a flow channel for the circulating liquid in an exterior device to be controlled in temperature are connected to a discharge port and a return port of the conduit, respectively, is generally known as disclosed, for example, in Patent Document 1 and so on.
FIG. 6 is an explanatory drawing showing a configuration of an example. A constant temperature liquid circulating device 40 in FIG. 6 includes a tank 41 for storing temperature controlling liquid, a conduit 42 having a discharge port 42a and a return port 42b for allowing the temperature controlling liquid in the tank 41 and circulating liquid at a constant temperature, which is heat-exchanged via a heat exchanger 43, to pass through a piping 51 of an external device 50, and a pump 44 provided in the conduit 42 for delivering the constant temperature circulating liquid to the piping 51 of the external device 50, wherein temperature sensors 46, 47 for detecting the temperatures (T1, T2) of the circulating liquid are provided at the discharge port 42a and the return port 42b of the conduit 42 so that a controller 48 for monitoring the temperature thereof controls the temperature of the circulating liquid.
In such a constant temperature liquid circulating device 40, as a method of controlling temperature in the related art for controlling the discharge temperature (T1) of the circulating liquid at the discharge port 42a of the conduit 42 at a preset temperature, there is a method in which the flow amount of the circulating liquid is kept constant, the circulating liquid is cooled/heated in the heat exchanger 43 in the tank 41 by an amount corresponding to the return temperature (T2) of the circulating liquid raised/lowered by the variations in heat load of the external device 50, so that the discharge temperature (T1) is controlled to be the preset temperature.
In this case, it is desired for the external device 50 to reduce the variation in temperature between the exit and entrance of the circulating liquid in the piping 51 (ΔT) to stabilize the temperature of the external device itself. However, since the flow amount is constant, the return temperature (T2) varies significantly according to the heat load as shown in FIG. 7, and hence the temperature change between the exit and entrance (ΔT) varies significantly in accordance with the variation of the heat load. Consequently, the temperature of the external device itself also varies significantly in the nature of things.
On the other hand, it is desired for the constant temperature liquid circulating device 40 to reduce variations in return temperature (T2) of the circulating liquid and stabilize the temperature in the tank 41 so that the discharge temperature (T1) is stabilized. However, in fact, the return temperature (T2) is changed by the heat load significantly as described above and hence the fluctuation in the discharge temperature (T1) is increased as shown in FIG. 7, whereby it takes time until it is stabilized.
In the constant temperature liquid circulating device 40 in FIG. 6, in the method of controlling temperature in the related art in which the return temperature (T2) of the circulating liquid in the return port 42b of the conduit 42 is controlled by the preset temperature, it is desired to keep the flow amount of the circulating liquid constant and cool/heat the circulating liquid in the heat exchanger 43 by an amount corresponding to the return temperature (T2) of the circulating liquid raised/lowered by the variations in heat load of the external device 50, so that the return temperature (T2) is controlled to be the preset temperature.
In this case, it is desired for the external device 50 to reduce the variation in temperature between the exit and entrance of the circulating liquid (ΔT) as described above and stabilize the temperature of the external device itself. However, since the flow amount is constant, the return temperature (T2) is significantly changed according to the heat load, and then, in order to keep the return temperature (T2) constant, the width of lowering/rising of the discharge temperature (T1) must be increased. Consequently, the variation in temperature between the exit and entrance (ΔT) is increased as shown in FIG. 8.
On the other hand, it is desired for the constant temperature circulating device 40 to minimize the width of lowering/rising of the discharge temperature (T1) for controlling the return temperature (T2) of the circulating liquid is minimized. However, as described above, since the fluctuation in the return temperature (T2) when the load is varied is increased (see FIG. 8), the width of lowering/rising of the discharge temperature (T1) for keeping the return temperature (T2) constant must be increased and, in addition, it takes time for stabilizing the return temperature (T2).
Since all the circulating liquid in the tank 41 is lowered/raised within a wide temperature width, excessive energy is required.
Japanese Unexamined Patent Application Publication No. 9-325821